Flowability of fine, highly cohesive calcium carbonate powder was
improved using high energy mixing (dry coating) method consisting in
coating of CaCO3 particles with a small amount of Aerosil nanoparticles
in a planetary ball mill. As measures of flowability the angle of repose
and compressibility index were used. As process variables the mixing
speed, mixing time, and the amount of Aerosil and amount of isopropanol
were chosen. To obtain optimal values of the process variables, a
Response Surface Methodology (RSM) based on Central Composite Rotatable
Design (CCRD) was applied. To match the RSM requirements it was
necessary to perform a total of 31 experimental tests needed to complete
mathematical model equations. The equations that are second-order
response functions representing the angle of repose and compressibility
index were expressed as functions of all the process variables.
Predicted values of the responses were found to be in a good agreement
with experimental values. The models were presented as 3-D response
surface plots from which the optimal values of the process variables
could be correctly assigned. The proposed, mechanochemical method of
powder treatment coupled with response surface methodology is a new,
effective approach to flowability of cohesive powder improvement and
powder processing optimisation.